Thanks for the response. Eventually I used the first option which is by
Whenever there is no data, the AsyncCallBack calls scheduleOnce() with some
poll interval and the onTimer() delegates to the method that does a DB
It's a nice, clean solution, and there's a good example of it in the new Akka
under the "Timed and Non-blocking polling" section.
On Thursday, September 8, 2016 at 9:59:42 AM UTC+3, gor...@8kdata.com wrote:
> Hi there,
> I am just a newbie on Akka, but as far as I know, you have to expect to
> not recive a new call to onPull until you push something. So you need an
> external "agent" to wake up your GraphStage. One option is to use a timer
> that each time it is executed, it queries the database and, if something is
> found and the outlet is ready (on java DSL, which is the one I use, the
> method is called *isAvailable*). Another option could be to use the
> reactive mongodb driver, open a tailable cursor and then all the magic
> should be automatically done for you. This second option sounds better, but
> I have never used that driver and I don't know if you can use a tailable
> If you decide to use the polling version, there I recommend you to check
> the samples on the documentation or even better, to check the Akka Stream
> source code. I am not used to read scala code, but I was able to understand
> the standard flow stages on the github repository, so I am sure you can do
> El miércoles, 7 de septiembre de 2016, 10:37:07 (UTC+2), Ori Popowski
>> We have a GraphStage[SourceShape[?]] with a simple OutHandler which does
>> the following:
>> 1. Finds a document in MongoDB
>> 2. Pushes that document to the outlet using push()
>> It's possible that the source will not find any documents in the DB at a
>> given moment, but new documents may be arrive later.
>> The problem is that after the first time onPull is called and doesn't
>> push anything to the outlet, then even when new documents are available in
>> the DB, they won't be pushed later.
>> It's like the notion of a demand from downstream just gets lost. I'm
>> obviously missing some API capability to deal with such situation, but I
>> cannot find any material on this.
>> How should we solve such a problem?
>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>> Check the FAQ:
>>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
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